The present invention relates to an elongated electroluminescence element (hereinafter referred to as "EL element") and a method of manufacturing the elongated EL element.
An EL element useful as a face light source for various display instruments is known as shown in FIG. 6 of the accompanying drawings. The known EL element 1 comprises a substrate which is generally composed of a back electrode 2, an insulating layer 3 formed on one side of the back electrode 2, and a luminescent layer 4 formed on the other side of the insulating layer 3. The back electrode 2 is formed of, for example, an aluminum foil. The insulating layer 3 contains dielectric powder such as, for example, barium titanate (BaTiO.sub.3) or the like. The luminescent layer 4 contains fluorescent material such as, for example, zinc sulfide (ZnS) or the like. A transparent conductive film 5 is provided which is formed is such a manner that indium tin oxide (ITO) is vacuum-deposited onto one side of a polyester film or the like. The transparent conductive film 5 is thermocompression-bonded onto the luminescent layer 4 of the substrate such that the vacuum-deposited ITO membrane is in contact with the luminescent layer 4. Subsequently, an assembly of the substrate and the transparent conductive layer 4 is sealingly covered with a pair of dampproof films 6 and 6 by means of thermocompression bonding or the like. Thus, the EL element is formed. The arrangement is such that when voltage is applied between the back electrode 2 and the transparent conductive film 5, an electric field is generated in the electroluminescence material consisting of the insulating layer 3 and the luminescent layer 4 whereby the luminescent layer 4 luminesces.
In case of an EL element having a relatively large surface area, the larger the distance from a pair of electrode terminals connected respectively to the back electrode 2 and the transparent conductive film 5, the higher the voltage drop. In order to prevent such voltage drop, conductive metal such as, for example, Ag or the like is deposited, by means of mask-printing or the like, onto the side of the transparent conductive film 5 which is in contact with the luminescent layer 4, to form an auxiliary electrode 5a. The auxiliary electrode 5a is bonded to the luminescent layer 4 by means of thermocompression bonding.
Thus, the auxiliary electrode 5a enables a predetermined voltage to be applied substantially over the entire region of the transparent conductive film 5, so that the EL element 1 can luminesce uniformly over its entire surface.
If it is desired to manufacture a particularly elongated EL element, however, the following problems arise. That is, there is a limit in the dimension of a mask plate which is employed when the auxiliary electrode 5a is formed on the transparent conductive film 5 by means of the mask-printing, so that it is difficult to manufacture an extremely elongated EL element. In this connection, it may be considered to utilize a printing apparatus which is capable of continuously printing the auxiliary electrode 5a. However, such printing apparatus is expensive, resulting in an increase in the manufacturing cost of the EL element.